Depletion of CD4+ and CD8+ T lymphocyte subpopulations by CIA-1, a chicken infectious anemia virus.

The suppressive effect of chicken infectious anemia virus (CIAV) on T-lymphocyte subpopulation was evaluated in vivo by flow cytometry and dual immunostaining on frozen sections. Between 14 and 21 days postinoculation (PI), the percentage of CD4-, CD8-, and CT1-positive (CD4+, CD8+, and CT1+) cells was significantly lower in chickens infected at 1 day of age with CIA-1 strain of CIAV than in controls. The mean percentage of CD4+ cells in the thymus was only 43%, whereas in the controls it was 77%. The mean percentages of CD8+ cells in the thymus in infected and control chickens was 54% and 90%, respectively, and of CT1+ cells, 44% and 92%, respectively. At 28 days PI, the percentage of CD4+, CD8+, and CT1+ cells was similar in infected and control chickens. Also at 14 and 21 days PI, immunoperoxidase staining demonstrated fewer CD4+, CD8+, and CT1+ cells in the thymus of infected chickens than in controls. In frozen sections of thymus stained with CIA-1 antibodies and CD4, CD8, or CT1, few of the cells positive for CIAV antigen seen in the outer zone of the cortex carried CD4, CD8, or CT1 molecules. These results suggest that CIA-1 infection either destroys cells expressing CD4, CD8, or CT1 molecules on their surface or interferes with the expression of these molecules.